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CVE Record

CVE-2021-47353: udf: Fix NULL pointer dereference in udf_symlink function

In the Linux kernel, the following vulnerability has been resolved: udf: Fix NULL pointer dereference in udf_symlink function In function udf_symlink, epos.bh is assigned with the value returned by udf_tgetblk. The function udf_tgetblk is defined in udf/misc.c and returns the value of sb_getblk function that could be NULL. Then, epos.bh is used without any check, causing a possible NULL pointer dereference when sb_getblk fails. This fix adds a check to validate the value of epos.bh.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel reliability bug in the UDF filesystem code. A failed block lookup can leave a NULL value that is later used, potentially crashing the kernel. The sources do not provide CVSS, exploit evidence, or a complete attack path, so business urgency depends on whether affected systems process UDF filesystems.

Executive priority

Treat this as a targeted kernel maintenance item, not an emergency based on current evidence. Prioritize patch verification where UDF content is handled, because kernel crashes can disrupt availability even without data theft or privilege escalation evidence.

Technical view

In udf_symlink, epos.bh receives the return value from udf_tgetblk, which can be NULL via sb_getblk failure. The vulnerable code used epos.bh without validation. The upstream fix adds a NULL check. Affected records point to Linux kernels from 2.6.12 through fixed stable lines around 4.4.276, 4.9.276, 4.14.240, 4.19.198, 5.4.133, 5.10.51, 5.12.18, 5.13.3, and 5.14.

Likely exposure

Exposure is most likely on Linux systems running affected kernels with UDF filesystem functionality reachable. Systems that mount or process optical media, disk images, or other UDF-formatted content deserve priority review. The source bundle does not identify specific distributions, configurations, or remote exposure conditions.

Exploitation context

The CVE is not listed as KEV, and the supplied sources do not report active exploitation. The described failure is a NULL pointer dereference in kernel filesystem code, commonly a denial-of-service class issue, but the bundle does not prove exploitability conditions or impact beyond the crash-risk pattern.

Researcher notes

The record lacks CVSS, CWE, and detailed exploit prerequisites. Analysis should stay close to the upstream fix: missing NULL validation after udf_tgetblk in udf_symlink. Validate affected status through vendor backports and the listed stable commits; avoid assuming remote reachability or active exploitation.

Mitigation direction

  • Update to a vendor kernel containing the referenced UDF NULL-check fix.
  • Confirm distribution backports rather than relying only on upstream version numbers.
  • Prioritize hosts that mount or inspect UDF media or filesystem images.
  • Where UDF is unnecessary, restrict its use according to vendor guidance.

Validation and detection

  • Inventory Linux kernel versions across servers, workstations, appliances, and containers hosts.
  • Check vendor advisories for inclusion of the referenced stable kernel commits.
  • Identify systems where UDF filesystems can be mounted or automatically processed.
  • Review kernel crash reports for UDF-related NULL dereference patterns.
Prepared
Confidence
medium
Sources
11

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2021-47353 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
2ADP providers
10Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2unaffected
LinuxLinux2.6.12, 0, 4.4.276, 4.9.276, 4.14.240, 4.19.198, 5.4.133, 5.10.51, 5.12.18, 5.13.3, 5.14affected
Weakness

CWE details

No CWE listed

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